Fundamental problems with the Shuttle, ISS, and Constellation:
Part 2 of 7 part series
Part 1: On The Proposed NASA Budget
Part 2: Understanding Current NASA Structure: Space Race to the Shuttle
The first problem with the Shuttle was in the switch in design that had to come about when we originally decided not to build a Space Station and a Shuttle. See, the Space Station was supposed to be this giant space laboratory in which we'd learn all this neat science about how things work in space. But since we didn't have the Space Station, we had to build the Shuttle to contain a laboratory where we could conduct all this neat science to learn about how things work in space.
Think about how efficient it would be to drive an RV every morning to work-- and then work in an office built in your RV. That's the difference between the Shuttle with no Space Station and the Shuttle with Space Station-- the original shuttle concept was more like a pickup-truck for space, where you could bring supplies and stuff to the giant space laboratory. The shuttle that was built was a giant RV that could go to the site and work from there, in addition to trucking a heavy load. Just as it's more expensive to drive an RV because its' bulkier, same deal with space travel-- except with space travel, the difference in fuel is exponentially bigger, and astronomically more expensive to start with. But we thought over time we could recoup that cost by the money we were going to save by the shuttle being reusable. Those savings never really showed up.
We started to understand why in the 90's, when we started looking at designing a Shuttle replacement, i.e. designing a better, cheaper, Shuttle, and looking at why the Shuttle was in fact getting more expensive to operate, not less. There were several projects with this aim, but the one that got furthest along was the VentureStar program by Lockheed. Ultimately, none of these programs took off, though, because none of them could be shown to save money over the Shuttle program over any period of time. In looking at why this is, it turns out that reusable launch vehicles just aren't cheaper than single-use vehicles. The reason for that is two-fold: launch, and re-entry.
On launch, a vehicle is riding through the second-most challenging environment man has ever experienced-- strapped to a big-ass rocket accelerating at ungodly speeds. Big rockets are so loud they can crack a plate of steel simply by the force of the sound they make. It's not just the acoustic loads-- rockets shake violently. If you were to put your car on top of a rocket, even ignoring acoustic vibration, it would shake itself apart in 5 minutes flat, and about 5 minutes after that it's welded steel frame would shake itself apart. This is not to mention that meanwhile the rocket is accelerating at about 10g's, so the raw mass of whatever you put on top of the rocket wants to rip apart simply because it is so heavy. To go back to the car on top of the rocket idea, at the same time your car was shaking itself apart, it would also be collapsing under it's own weight.
But say you survive launch; the environment of Space is fairly ideal, if you can handle a couple simple problems. Ever notice how so many of your basic physics problems focused on something happening in zero-g, with no atmosphere? Space has some unique challenges, but generally in terms of hardware life it can be more forgiving than a nasty planet with a gravity field and atmosphere and grime and grit to get into the gears. For a reusable vehicle, though, you have to come back down-- which means re-entry.
Re-entry is just barely more hostile than launch, winning the title of the most challenging environment man has ever experienced. The deceleration is not quite as bad as the trip up. The vibration and the sound (acoustic loads) are as bad-- generally you start to enter the atmosphere at super-sonic speeds, because the cheapest way to do reentry is just to let the air of the atmosphere slow you down as you fall down the earth's gravity well at a carefully calculated angle. Actually, technically at re-entry you enter the atmosphere going so fast that we invented an entirely different term for it-- HYPER-sonic. Put this in perspective: in re-entry the Space Shuttle reaches Mach 18 (Technically it leaves at Mach over that, but that is in a very thin atmosphere). The fastest jet flys at something like Mach 3 or 4. The Waverider hits around 6 or 7, but is still mostly experimental. At this Mach (hypersonic) friction with the air causes so much heat that the air itself starts burning and producing more heat, in fact at one point during re-entry the shuttle is surrounded in a bubble of air heated to form a plasma shock and is entirely reliant on computer controls-- because it is surrounded by a cloud of ionized plasma which prevents remote control and in atmospheric turbulence which is too choppy for manual control. This is why the shuttle needs to be covered in specialized ceramic tiles, and why the bottom of the Apollo capsules were covered in the same. So while the acoustic, acceleration, and vibration environment are comparable to launch, on TOP of that you also have this ungodly thermal problem, which is why re-entry takes the cake over launch.
With a reusable launch vehicle, though, the proposal is to re-use hardware that has been through those two wild rides-- possibly multiple times. The trouble is, though, that most hardware doesn't survive these environments very well. Hairline cracks develop which could be catastrophic in most metal and ceramic components-- the bulk of the functional bits of the vehicle. More tricksome is that pretty much every component is critical to the vehicle-- space systems design is so sparse that there isn't much redundancy of design where it can be helped. So if any of these components is damaged either in launch or re-entry, this could be catastrophic. Meaning that between uses, you have to comb over every component of the vehicle, examine them, verify that the ones that are still reusable are safe, replace the ones which were damaged, and then reassemble the vehicle. The more uses the vehicle has seen, the more components will need to be replaced.
With the Shuttle, this turns out to be more expensive than if we had just stuck with the Apollo/Titan based space program and launched more SkyLabs. Reusable launch vehicles are more expensive than single use vehicles for this reason. It's cheaper just to build a brand spanking new single-use rocket with all new parts than it is to tear apart the Shuttle after every mission, examine all it's parts, replace those that need fixing, verify those that don't, and then put it back together again. Imagine if you had to rebuild that RV's engine and detail the exterior every time you took a road trip.
The other problem came to be with the International Space Station (ISS). The first problem is that by the point it's finished, the ISS won't actually be all that useful in terms of gathering scientific data. What we didn't know about human physiology in micro-gravity when the ISS was still working out it's international funding, the Russians learned a lot about with MIR-- and the Russians were willing to share that info with us. Not to mention that we've learned a lot about other things you can learn on a space station-- on the space station in it's incomplete form.
There's still valuable science to be had, but nothing that really says much about long-term human survival in space that we don't know already. It's a nice, big, giant laboratory in space, and it will give us nice information about space stuff, like growing food in orbit and give us a platform for testing new ways to deal with muscle atrophy and bone softening for long-term microgravity missions, and maybe we can discover some other last little bits about human physiology in space... but yeah. It's not ground breaking science, it's not likely to produce anything which will change the way we look at the universe. Put it this way-- it's like spending all the money that was put into decoding the human genome into learning about the genome of sea turtles instead. It will provide a lot of valuable scientific data, but nothing that will have a fundamental impact on humanity the way that knowing our own genetic code will one day mean.
More critically, the ISS tells us NOTHING about going to other planets, like say, Mars.
Mars is another planet, with it's own gravity field that is less than Earth, but more than the Moon, and exactly nothing like the gravity environment found in low earth orbit. To boot, the Moon and Mars have lots of weird space dust that gets into just about everything. We know about jack shit about long-term human survival in partial gravity-- when we went to the moon, we pretty much landed, planted a flag, and left. Then we went back, drove around our cool rover for a bit, planted more flags, picked up some moon rocks as souvenirs, and then went home. We were never on the surface of the moon for more than a few days. Using conventional technology (i.e. existing technology today), if we went to Mars, we'd have to survive on it's surface for about 2 years. A few days isn't anything like two years. That's why Constellation was supposed to take us back to the Moon: so we could understand more about how to actually survive for 2 years on Mars.
Beyond that, the ISS is in low earth orbit, meaning that it is protected from two massive sources of radiation by the Earth's magnetic field-- protection we wouldn't have on the journey from Earth to Mars, and on the journey from Mars to Earth, and protection that would be less robust in Mars orbit and on the Mars surface. Those massive sources of radiation are two fold, and either is enough to kill a human crew, either slowly through radiation poisoning, or in about 5 seconds flat in an intense burst that fries the crew.
The first of these is the solar flare. This is basically when the sun chunks a big wave of superheated plasma outward in a big giant burp of ionized particles traveling at sub-light speeds. This is why we didn't stay on the Moon for long-- in the 60's and 70's we didn't know much about radiation shielding or all the types of radiation to be encountered in space, but we did know about solar flares. If a solar flare had occurred during any of the Apollo missions, every last member of the crew would have been fried, and everyone in the biz knew it. Keeping the journey short kept the danger lower, but still high. We don't really know much about solar flares or how they occur, though we are starting to. Predicting them is like predicting the weather, only less accurate. When one occurs, we get about 3 minutes worth of warning from the satellites we have in place now, and that reaction time is limited by the speed of light.
Then there's the constant cosmic background radiation-- the radiation produced by a universe full of nuclear-reacting stars, supernovas, black holes, plasma nebulae-- the list goes on. Basically, Earth's magnetic field is a nice buffer against all the junk radiation thrown out by the rest of the universe that comes our way. Cosmic radiation is not only high, but pretty constant, meaning that you have to carry a lot of good shielding-- and different types of radiation call for different shielding, most of which has one thing in common: it's heavy. Meaning you've got to schlep all this extra mass around to protect your human crew from radiation poisoning.
But we're tied to the ISS, by international agreement. That's why the Constellation plan was to dump the Space Station as soon as humanly possible, which turns out to be shortly after we complete it. The Space Station requires a huge cost outlay in terms of support staff-- you've got to get all the equipment to do the experiments in your space laboratory, plus all the supplies for the crew, and you have to switch out crew. Plus you've got to do orbit maintenance, and make sure that you don't run into space debris (THANK YOU, China and Soviet Russia!) and maintain all the hardware and stuff like that. And you've got to pay all the salaries of the people who are qualified to do all of this. That's a lot of money to spend on some not-so-exciting science, when you could be investing it in some much more ground-breaking work.
Constellation was the next major step, which would have sent us first back to the Moon, so that we could understand more about surviving on Mars for two years, and then on to Mars itself. The moon is a lot more like Mars than empty space-- it has weird dust problems, it has partial gravity. But unlike just going to Mars, we can get back from the Moon real fast, and we can communicate with the Moon in near-real time. Meaning that if something goes wrong with the astronauts, they're not far from home, and easier to monitor. We could learn everything we need to know about partial gravity's effects on human physiology close to home, figure out how to deal with space dust (close to home), and the radiation problem (close to home).
Constellation would also have helped us understand how to assemble large space-mission vehicles in space. To get to the Moon the first time, we launched the lander separate from the capsule containing the astronauts and the rocket which sent the whole shebang from Earth orbit to the Moon. To get to Mars using existing technology, we'd have to assemble a much larger space vehicle in orbit, with a much bigger rocket. To do that using conventional (read: current) rocket technology, we needed a lift vehicle capable of lifting something heavier than the Space Shuttle's lift capacity-- which delivers a heavier payload to orbit than any other rocket out there today. In other words, we had to build the biggest rocket ever.The idea behind the Ares rocket family, which Constellation centered around, was to re-use a bunch of existing Shuttle hardware and infrastructure to build a better vehicle.
This was useful for few reasons:
(a) Building infrastructure ain't cheap. If you can re-use, say, the same solid-fuel boosters the Shuttle uses, and all the other parts of infrastructure that are used in in putting together the Shuttle, you save money because you don't have to build all new stuff. That money adds up real quick.
(b) Reusing infrastructure and components means a faster turn around time. It's embarrassing for the USA, who won the space race, to not have human access to space. It'd be like Google going down for a month for upgrades. The idea was that we wanted to minimize the down time.
(c) It's also good politics. Shutting the shuttle program means that the people whose careers were dedicated to shuttle hardware either have to retire or move on. That's technically a loss of 7,000 jobs of technicians and such. Those people will in the short term have to seek new employment-- though frankly in the long term they're likely to find it, just probably not in Florida.
(d) That poses a HR problem, though:The trouble then is that when you get your manned space program up and running again 5 years down the line, you then have to go rehire them from their interim employers, and some of them will have retired, meaning that your senior people are now the junior people from the last time you had a manned program, and they haven't had any work in the field for a few years. Plus you've got to hire them away from the people they end up working for after the Shuttle Program shuts down.
The trouble with Ares was that it was admittedly a rush job. Rush jobs and space don't necessarily go well together-- either you end up incredibly expensive, like the Mercury/Gemini/Apollo programs (rush jobs if there ever were any), or you end up with a catastrophic failure, or both (Apollo had both-- remember, the crew of Apollo 1 died in a test firing accident). Two problems with that now are obvious: (a) we're in a recession, and it will probably be years before our economy fully recovers, and (b) we're much less tolerant of catastrophic events than we were during the Apollo days. There's no overwhelming security concerns to consider. The only rush is that China might get back to the Moon before we do-- but that has no security impact. Meanwhile, another event like the Columbia disaster could sink US human space access for a decade or more.
Meanwhile, NASA's greatest successes over the past 20 years have been in unmanned missions. There's the Mars Rover program. There's Hubble (though Hubble is so reliant on the Shuttle that it's better thought of as a half-manned mission). There's COBE, and the mapping of the Big Bang. There's the probes of other planets. All of these were put together on a shoestring budget in comparison to the Shuttle and Station programs. Technically the ISS is a huge achievement of the Shuttle program, but in public eye the success of the ISS tends to be separated from the Shuttle itself, much as Hubble is seen as separate from the Shuttle even though Hubble needs to be serviced periodically by the shuttle in order to remain active. Overall, realistically, you get more useful science for your buck in the unmanned stuff, especially in earth orbit stuff-- for now. We've also learned that catastrophic losses in unmanned systems are more acceptable than loss of astronauts-- the loss of Columbia was far more devastating in terms of PR than the loss of a few Mars probes.
Also in the interim, Space has gone commercial. NASA's no longer the only space-show in the US.